Police have scheduled a news conference this evening and WTOP will bring you more information as it becomes available.

EARLIER: Tuesday – 4/23/2013, 1:23pm ET

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Newell (Courtesy Metropolitan Police Department)

UPPER MARLBORO, Md. – An off-duty D.C. police detective is dead in what authorities call a “domestic-related homicide,” and police are searching for the victim’s stepson in connection with the killing.

Prince George’s County police say Joseph Burrough Newell, 46, was shot and killed Monday night at a home on Green Moss Drive in Upper Marlboro, Md.

Police were called to the home at 8:13 p.m., and Newell — who joined the Metropolitan Police Department in 1989 — was pronounced dead at the scene.

Police have issued a warrant in connection with the incident for 27-year-old Antwan Rayvon James. James is Newell’s stepson and also lived at the home in Upper Marlboro. Authorities say he recently was fired from the D.C. Fire and EMS Department.

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James (Courtesy Prince George’s County Police Department)

He also has an outstanding warrant for assault. It was issued March 16, officials say.

Police say the incident stemmed from a dispute centered around yard work. Newell reportedly was on a stepladder screwing in a light bulb and asked his stepson for help.

“The stepson, James, didn’t like it and shot and killed his stepfather,” Prince George’s County Assistant Police Chief Kevin Davis says. “It’s as simple and tragic as that.”

Police described the incident as an execution, and say the shooting was captured by surveillance cameras.

James is described as a black male, about 6 feet tall and 170 pounds. He was last seen wearing a white T-shirt, blue jeans and black boots. Police think he may have a gun and say he should be considered dangerous.

After arriving on the scene, police initially thought a suspect still might be there and urged neighbors to stay inside their homes. K-9 officers and specialized teams now are searching for James.

“It is believed the suspect is no longer in the residence and may not be in the immediate area,” Prince George’s County police spokeswoman Cpl. Maria McKinney says. “We are actively searching for that person.”